Dermatoglyphics

The DG patterns of these patients were recorded for all 10 digits of the hands using a Green Bit Dactyscan^® 84C fingerprint reader (Fulcrum Biometrics, Haryana, India) and categorized into loops, whorl, and arch, with their subtypes based on the modified classification¹³ (Figure 1), as follows:

1. Loops: One or more ridges entering from one side and exiting from the same side comprises a loop. All loops have one delta. Loops were subclassified as single loop or double loop.

2. Whorl: Must contain at least two deltas and a type line. One ridge must complete the circuit. Ridge may be spiral, oval, or any variant of a circle.¹⁴ The whorl was further subdivided into symmetrical and spiral whorls.

3. Arches: They do not have a type line, deltas, or cores. Simple arch is the simplest and constitutes ridges extending from one side of the print to the opposite side at the center of the pattern, thus forming a wave-like structure. The tented arch is similar, but rises sharply in the center, causing a thrust/spike, or the ridges meet at an angle less than 90°.¹³

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Cast Analysis

Good pretreatment casts of all the patients with a complete set of maxillary teeth with or without third molars were scanned using a inEos X5^® 3D cast scanner (Sirona Dental Systems GmbH Fabrikstraße 31, 64625 Bensheim, Germany). The palatal area on the 3D images was examined on the computer screen using Minimagic 2.0 software (Materialise, Technologielaan 15, 3001 Leuven, Belgium).

The global coordination system in Rhino 5 software (McNeel Europe Roger de Flor, 32-,34 Barcelona, Spain) was used to orient all the cast images with the X-axis in line with the midline of the palate and the Z-axis in line with the frontal view (Figure 2).

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Palatal Area (PA) Calculation

After orientation, the casts were transferred to another Meshmixer software (Version 3.5, Autodesk Inc, San Rafael, California, USA) for PA calculation in mm by extracting the palatal surface from the image (Figure 3). This was achieved by creating a closed loop by drawing a starting line at the distal end of the gingival contour of tooth 16 up to the distal end of tooth 26. Then this line was extended anteriorly along the free gingival margin of the anterior teeth and back up to the starting point. This selected area was then raised 11 mm from the original meshwork using the “extract” command. Finally, the area of this extracted palate was calculated using Rhino 5 software.

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Intercanine Distance (ICD) and Intermolar Distance (IMD) Measurement

ICD was measured as the distance between maxillary canine cusp tips or estimated cusp tips in attrited teeth. IMD was measured as the distance between the mesio-buccal cusp tips of the maxillary first molars or the estimated cusp tips in attrition cases.¹⁵ ICD and IMD were measured using the “distance” tool of Minimagic 2.0 software in an axial view between the respective points on the teeth, as described.

Palatal Height (PH) Calculation

PH was measured (in millimeters) as the length of the perpendicular line from the deepest point on the palate on the midpalatal raphe joining a straight line from the deepest portion of gingival contours of teeth 16 and 26.

Statistical Analysis

All of the variables were analyzed by different observers having competence in analyzing DG pattern and utilization of 3D software to analyze maxillary arch parameters. Interobserver bias was evaluated using Kappa statistics (kappa index = 0.92). Skewness and kurtosis estimates for the dependent measures were within acceptable limits (skewness/standard error < 2.00).

Comparison of the three malocclusion classes (I, II, III) with DG patterns was done using Kruskal-Wallis analysis of variance (ANOVA), and comparison with PD was by one-way ANOVA. Spearman's rank correlation was used to assess the relationship between DG and PD, and ordered logistic regression was used to assess their predictive capability for malocclusion.

Dermatoglyphics and Angle Malocclusions

There exists extensive literature on the genetic determinant of fingerprint patterns in every individual. The gene responsible for formation of fingerprints is known to be the SMARCAD1 gene, located on 4q22.3 [long (q) arm of chromosome 4 at position 22.3]. The SMARCAD1 gene provides instructions for making a unique skin-specific isoform for each individual, which is expressed only in skin cells and appears to play a critical role in the formation of DG. These ridges are also present on the toes, the palms of the hands, and the soles of the feet. It develops before birth and remains the same throughout life.²¹

The gene strongly associated with malocclusion has been identified as the MSX1 gene. It is located on chromosome 4p16 and is expressed in cranial neural crest cells, thus influencing the development of the nasal processes, maxilla, and mandible.^22,23 Previous study²⁴ has confirmed an important correlation between the MSX1 gene and Class I and II malocclusions.

As a result of the close association of those two genes on the same chromosome, it can be hypothesized that malocclusion and fingerprint pattern have a relationship. It was observed that only the double loop characteristic showed a significant association with malocclusion (Table 2). This was similar to the results of Tikare et al.¹² They believed that sample size variations and an unclear protocol for fingerprint recording could contribute to varied results. An amalgamation of hereditary and environmental factors influences the abnormalities of fingerprint patterns. It was also proposed²⁵ that the underlying mechanism of variability in the DG pattern could result from factors such as inadequate oxygen supply, unusual distribution of sweat glands, and alterations of epithelial growth during intrauterine development. Another observation that the authors of this study came across was a common observation of heterogeneity of fingerprints in Class III malocclusion. This, by itself, may be a determinant factor in the development of malocclusion. It can be hypothesized that this variation in individual fingerprints may be an ultimate effect of an unknown stress during fetal development. Hence, DG may be a useful tool in trying to understand how genetic vulnerability interacts with the growth of Class III malocclusion.

In this study, an increased frequency of tented arch in all three malocclusion groups was found, which is consistent with observations by Reddy et al.²⁶ Their results showed Class II and Class III malocclusions to be associated with a high number of arches and loops. In addition, the current study results were consistent with those of Trehan et al.²⁷ They observed that Class II malocclusion was significantly associated with an increased frequency of arches. Thus, the association between malocclusion and DG pattern has been documented by only a few studies.^25,26,28

Palatal Dimensions

There has been no reported literature on the association of DG parameters with PD. Hence, the current study explored this novel idea of correlation to help predict patients' palatal dimensional characteristics using DG pattern. The classification used in DG analysis may further be utilized as a reliable criterion for correlating PDs.

The association of malocclusion and PD has been studied previously⁸ comparing normal occlusion with open and deep bite,²⁹ Class I and II malocclusions,³⁰ and Class I and III malocclusions.³¹ A study by Al-Sayagh²⁰ compared PD in four classes of malocclusion based on Angle classification in an Iraqi population. Malocclusion and PD were assessed in ethnically different populations by multiple authors^{12,15,20,29,32} who have documented varied results, thereby confirming the influence of ethnicity. The current study aimed at correlating PD and DG pattern in malocclusion classes. It was observed that there were no significant differences between any of the palatal anatomic parameters and Angle malocclusion groups except PA. This finding was in contrast with the previous literature.^20,32,33 Variations in sample size and absence of clear protocol in most previous studies might have contributed to contradictory results. A combination of hereditary, environmental, and local factors influences palatal anatomy. The variations would occur only when the combined factors exceed a certain threshold level.²⁶ Hence, the factors that are responsible for PD and malocclusion might not cross this threshold level for the clinical manifestation to occur. The current study was unique because it employed measurements on a 3D image rather than using a two-dimensional analysis.

The tendency toward decreased maxillary palatal area in Class I malocclusion (Table 1) was compatible with a multifactorial determination or gene/environment interaction. It can also be said that certain environmental factors may affect some genetically determined craniofacial phenotypes. This tendency could be explained, at least in part, by the interracial mixing of different populations, which is a feature of ‘globalization.' There is indisputable evidence for a significant genetic influence in many dental and occlusal variables, while phenotype is the result of both genetic and environmental factors.¹